Design and Evaluation of an Active/Semiactive Ankle-Foot Orthosis for Gait Training

Neuromusclar disorders such as stroke often cause walking impairments. During walking, the ankle joint contributes the largest propulsive moment and plays a vital role in shaping a normal gait pattern. The goal of this paper is to introduce a novel powered ankle-foot orthosis (AFO) for gait rehabilitation named Stevens Ankle-_Foot Electromechanical (SAFE) orthosis. Unlike other powered AFOs, the SAFE orthosis features two alternative actuation modes: fully-active and semi-active. The former employs two BLDC motors to provide plantar and dorsiflexion torques; the latter replaces the dorsiflexion side motor with a set of linear springs. This design provides a direct way to investigate how the introduction of a passive antagonistic element may affect the performance of a powered AFO. Initial results from bench testing indicate that the performance of the two actuation modes are comparable in terms of device transparency and torque tracking. Possible implications for the design of future powered AFOs are discussed in the paper.